The biological and clinical impact of inhibition of NF-κB-initiated apoptosis in diffuse large B cell lymphoma (DLBCL).

NF-κB is frequently over-expressed in a variety of non-Hodgkin's lymphomas (NHLs) and has been implicated in lymphomagenesis; however, its role in diffuse large B cell lymphoma (DLBCL) as a prognostic biomarker has not been fully elucidated. Therefore, we investigated the role of NF-κB and its association with clinicopathological features in a tissue microarray cohort of 230 DLBCL patient samples. We then elucidated the role of NF-κB inhibition on cell viability and apoptosis in vitro, using DLBCL cell lines. Using immunohistochemistry, NF-κB was detected in 25.6% (52/203) DLBCL tumours, was associated with activated B cell (ABC) phenotype (p = 0.0054), Epstein-Barr virus (EBV; p = 0.0080) and over-expression of the anti-apoptotic marker XIAP (p = 0.0013). DLBCL cases with nuclear expression of NF-κB showed a significantly poorer overall survival as compared to those without NF-κB expression (p = 0.0236). In a multivariate analysis using a Cox proportional hazard model for IPI and NF-κB expression, the relative risk was 2.97 for high NF-κB expression (95% CI 1.27-6.94; p = 0.0113) and 7.55 for the high-IPI group (95% CI 3.34-18.35; p < 0.0001). In vitro, Bay 11-7085 inhibited constitutively active NF-κB expression in a dose-dependent manner and inhibition of NF-κB also down-regulated expression of the downstream target gene products Bcl-2, Bcl-XL (BCL2L1), XIAP and Survivin, leading to apoptosis via activation of the mitochondrial apoptotic pathway. NF-κB over-expression was found to be an independent prognostic marker for poor survival in DLBCL. Altogether, these results suggest that NF-κB may be a useful prognostic biomarker and a potential target for therapeutic intervention in DLBCL.